Trifunctional Electrocatalysts with High Efficiency for the Oxygen Reduction Reaction, Oxygen Evolution Reaction, and Na–O2 Battery in Heteroatom-Doped Janus Monolayer MoSSe

Trifunctional electrocatalysts with high activity for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and Na–O2 battery are eagerly desirable for electrochemical energy applications. Currently, it remains challenging to achieve such trifunctionality on a single catalyst, although many systems can exhibit either one or two activities. Herein, on the basis of first-principles calculations, Ni-doped Janus monolayer MoSSe with superior electrocatalytic activity toward ORR for fuel cells and OER for water splitting is proposed. Both its ORR and OER display an ultralow overpotential, and the ORR possesses a high selectivity with the Faradaic efficiency approximating 100%. Importantly, it further shows high performance of Na–O2 batteries with a low overpotential of 0.49/0.59 V for ORR/OER, suggesting it being the excellent trifunctional catalyst. Such catalytic behaviors are largely due to the synergistic effect of the built-in electric field and heteroatom doping. These findings not only gain deeper insight into the catalytic activity of Janus monolayer MoSSe but also guide developing effective trifunctional electrocatalysts.